The invention relates to an exhaust gas turbine for a turbocharger having a spiral housing consisting of sheet metal.
An exhaust gas turbine for a turbocharger in which a spiral housing made from sheet metal is both fixedly connected to a contoured casing and clamped to a central bearing housing of the turbine via an intermediate ring by means of a clamping strip is known from WO 02/06637. According to one version of the exhaust gas turbine the intermediate ring can be designed integrally with the contoured casing or form a separate component. The spiral housing is composed of two sheet metal shells, of which one forms the spiral duct wall which faces the flow guide vane structure, while the other shell forms the outer spiral duct wall. The outer duct wall can be surrounded by another shell with an air gap for thermal insulation purposes. The spiral housing is of complicated design and is therefore complex in terms of manufacture and assembly. Furthermore, it is of considerable weight and in particular does not allow equalization of different thermal expansions of the individual housing parts relative to one another without considerable thermal stresses. Such thermal expansions can lead to malfunctions and result in premature wear. The adjusting mechanism for the guide vanes, a bearing ring for the guide vanes, the contoured casing and the guide vanes themselves can form a modular unit which can be preassembled.
A turbine housing for a turbocharger in which the spiral housing is of double-walled design is known from DE 100 22 052 A1. The inner wall which forms the spiral duct is attached by means of an inlet funnel, which opens tangentially into the spiral housing, to an inlet flange. The outer wall is welded to the inlet flange, while the inner wall has a sliding seat with respect to the outer wall and the inlet flange with a sliding seat, so that thermal expansions in the direction of the inlet funnel between the inner and outer wall do not generate thermal stresses. However, as a matter of principle, no equalization of the inner and outer wall of the spiral housing is provided in the axial direction of the exhaust gas turbine, so that, in the event of high temperature differences between the inner and outer shells in particular, durability can no longer be ensured on account of intense stresses.
It is the object of the present invention to provide an exhaust gas turbine having a two-shell turbine housing consisting of sheet metal parts which are simple and light and generate the smallest possible stresses under thermal influence.